5-Hydroxytryptamine does not release endothelium-derived relaxing factor in rat isolated coronary arteries.
Removal of the endothelium from isolated rat proximal and distal coronary artery segments shifted the 5-HT concentration-response curve to the left without affecting, the maximal contractile response. 5-HT had no relaxing effect in 10(-5) M prostaglandin F2 alpha-precontracted vessels with an intact endothelium in the presence of 10(-5) M ketanserin. The spontaneous myogenic tone increased in both proximal and distal coronary artery segments after the endothelium had been removed. Indomethacin (10(-5) M) reduced the response of the proximal coronary artery segments to 5-HT by 35% but indomethacin had no effect on the 5-HT concentration-response curve of the distal coronary artery segments. Indomethacin relaxed precontracted (40 mM potassium) proximal coronary artery segments independently of the presence of the endothelium, suggesting a non-specific relaxing effect of indomethacin in these arteries. It is concluded that rat coronary artery endothelium is unresponsive to 5-HT because it lacks 5-HT1 receptors. The increased 5-HT sensitivity and spontaneous myogenic tone of endothelium-denuded rat coronary arteries is probably due to the elimination of the relaxing stimulus mediated by spontaneously released endothelium-derived relaxing factor.
Nyborg
N C
NC
Department of Pharmacology, University of Aarhus, Denmark.
Mikkelsen
E O
EO
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D003331:Coronary Vessels / Q000187:drug effects / Q000378:metabolism*; D015237:Dinoprost / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000187:drug effects; D066298:In Vitro Techniques; D007650:Ketanserin / Q000494:pharmacology; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism*; D011189:Potassium Chloride / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D012701:Serotonin / Q000494:pharmacology*
D009569:Nitric Oxide; D012701:Serotonin; D011189:Potassium Chloride; D007650:Ketanserin; D015237:Dinoprost; D000109:Acetylcholine